Physics Commons^™

Density Functional Calculations On Single Molecular (1d) And Van Der Waals Bi -Layered (2d) Magnets., Md Shamsul Alam

Open Access Theses & Dissertations

Low-dimensional magnetic materials show novel properties that is not seen in bulk magnets. The weak interactions such as spin-orbit interactions, electron correlation, van der Waals interaction in case magnetic bi-layers, play an important role in determining the properties of the system. Using density functional theory, we computationally investigated two categories of magnetic material- 1: Single Molecular Magnets (SMM) 2: Van der Waals layered Cr-Halide magnets. We used different classes of density functionals to examine the spin ordering and magnetic anisotropy barriers in several single molecule magnets - Mn12, Co4, Ni4, V15. We find that the magnetic anisotropy barrier significantly depends …

Some Fermi-Lowdin Orbital Self-Interaction Correction Studies On Atomic Systems, Christopher Alexis Ibarra

Open Access Theses & Dissertations

Density Function Theory (DFT) is a popular quantum chemistry calculation method with many appeals but also deficiencies. Many modification and additions to the method have been made over the years, such as self-interaction corrections and new density functional approximations. We review here the theoretical background needed for a basic understanding of quantum chemistry calculations. In addition, we present the quantum chemistry calculation method used in this paper called Fermi-Lowdin Self-Interaction Correction (FLOSIC), including the base code it was implemented on, the Naval Research Laboratory Molecular Orbital Library (NRLMOL) Code, and the resulting modified code simply called FLOSIC. Furthermore, we explore …

Decay And Dissipation: Finding Energy Level Jumps In A Harmonic Oscillator System Using Fortran And Fourier Analysis, Clara Chilton

Scripps Senior Theses

In this paper, I will look at a mass-spring system that can be described by a Hamiltonian. In most systems described by a Hamiltonian, the energy levels will be quantized, and the system will be able to jump between them. However, many methods of finding these jumps aren’t well-suited to numerical analysis. I’ll use a Markovian approximation (The Liouville von Neuman Equation), which allows me to use only the last time step to find the current one. Using this, I will analyze the system to find the time evolution of the probability density matrix – whose diagonal shows the probability …

Development And Assesment Of Local Scaled Self-Interaction Corrected Density Functional Method With Simple Scaling Factor, Selim Romero

Open Access Theses & Dissertations

The Hohenberg-Kohn-Sham (HKS) density functional theory (DFT) is widely used to compute electronic structures of atoms, molecules, and solids. It is an exact theory in which ground state electron density plays the role of basic variable, same as the wavefunction does in quantum mechanics. The total ground state energy is a functional of electron density. The practical application of HKS DFT require approximation to the exchange-correlation energy functional. Many density functional approximations (DFAs) with various degree of sophistication and complexities have been developed. Depending on the complexity, these functionals include electron density, density gradients, density Laplacian, kinetic energy densities, Hartree-Fock …

Development Of Quantum Information Tools Based On Multi-Photon Raman Processes In Rb Vapor, Nikunjkumar Prajapati

Dissertations, Theses, and Masters Projects

Multi-photon nonlinear processes in atoms have served as important tools for quantum metrology, quantum communications, and quantum sensing. In this thesis, we experimentally address the interplay of various multi-photon Raman processes in hot Rb vapor, with the four-wave mixing (FWM) process being a central theme. FWM is the nonlinear response of a medium to a strong optical pump field inelastically scattering off atomic resonances and resulting in the generation of additional photons in different modes. FWM is a detrimental, but inherent part of electromagnetically induced transparency (EIT) and Raman based quantum memories. However, we were able to weaken the four-photon …

Magnetism In Γ-Fesi2 Nanostructures: A First Principles Study, Sahil Dhoka

Dissertations, Master's Theses and Master's Reports

First-principles calculations are performed on γ-FeSi₂ nanostructures grown on Si (111) and (001) substrate. An attempt to explain the origin of emergent magnetic properties of the metastable gamma phase of iron di-silicide (γ-FeSi₂) is made, which show ferromagnetic behavior on nanoscale, unlike its possible bulk form. Many papers try to explain this magnetism from factors like bulk, epitaxial strain, interface, surface, edges, and corners but doesn’t provide an analytical study for these explanations. Density functional theory is used to analyze the magnetic effects of these factors. The results for the epitaxial structures show no magnetic behavior for …

The Pion Form Factor And Momentum And Angular Momentum Fractions Of The Proton In Lattice Qcd, Gen Wang

Theses and Dissertations--Physics and Astronomy

Lattice Quantum Chromodynamics (QCD) provides a way to have a precise calculation and a new way of understanding the hadrons from first principles. From this perspective, this dissertation focuses first on a precise calculation of the pion form factor using overlap fermions on six ensembles of 2+1-flavor domain-wall configurations generated by the RBC/UKQCD collaboration with pion masses varying from 137 to 339 MeV. Taking advantage of the fast Fourier transform, low-mode substitution (LMS) and the multi-mass algorithm to access many combinations of source and sink momenta, we have done a simulation with various valence quark masses and with a range …

Theoretical Studies Of C And Cp Violation In $\Eta \To \Pi^+ \Pi^- \Pi^0$ Decay, Jun Shi

Theses and Dissertations--Physics and Astronomy

A violation of mirror symmetry in the $\eta\to\pi^+\pi^-\pi^0$ Dalitz plot has long been recognized as a signal of C and CP violation. In this thesis, we show how the isospin of the underlying C- and CP-violating structures can be reconstructed from their kinematic representation in the Dalitz plot. Our analysis of the most recent experimental data reveals, for the first time, that the C- and CP-violating amplitude with total isospin I = 2 is much more severely suppressed than that with total isospin I = 0.

In searching for C- and CP-violating sources beyond the SM, we enumerate the leading-dimension, …

Resource Efficient Design Of Quantum Circuits For Cryptanalysis And Scientific Computing Applications, Edgard Munoz-Coreas

Theses and Dissertations--Electrical and Computer Engineering

Quantum computers offer the potential to extend our abilities to tackle computational problems in fields such as number theory, encryption, search and scientific computation. Up to a superpolynomial speedup has been reported for quantum algorithms in these areas. Motivated by the promise of faster computations, the development of quantum machines has caught the attention of both academics and industry researchers. Quantum machines are now at sizes where implementations of quantum algorithms or their components are now becoming possible. In order to implement quantum algorithms on quantum machines, resource efficient circuits and functional blocks must be designed. In this work, we …